In a large city school system with 35 elementary schools the school board is considering the adoption of a new policy that would require elementary students to pass a test in order to be promoted to the next grade The PTA wants to find out whether parents agree with this plan Listed below are some of the ideas proposed for gathering data For parts a through d indicate what kind of sampling strategy is involved and what if any biases might result Assume the schools are homogeneous and differ from each other OC Bias could result only if the sampling strategy is not followed as described OD Nonresponse bias could result since not all parents will respond d Mail a survey to the home of every student and ask parents to fill it out and return it within a week Which kind of sampling strategy is involved OA Convenience sampling OB An attempt at a census OC Stratified sampling OD Cluster sampling What kind of bias if any is most likely to result OA Nonresponse bias could result since not all parents will respond OB Response bias could result since the PTA wants parents to agree to this plan OC Voluntary response bias will result since only parents who feel strongly about the issue will respond